Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$118.98	8.556%	$129.1599	$129.16	$129.15	$129.20
Purchase #2	$150.69	6.396%	$160.3281	$160.33	$160.35	$160.30
Purchase #3	$59.50	3.561%	$61.6188	$61.62	$61.60	$61.60
Purchase #4	$32.97	13.644%	$37.4684	$37.47	$37.45	$37.50
Purchase #5	$6.60	7.555%	$7.0986	$7.10	$7.10	$7.10
Purchase #6	$43.32	6.334%	$46.0639	$46.06	$46.05	$46.10
Purchase #7	$36.40	3.553%	$37.6933	$37.69	$37.70	$37.70
7 purchase totals =	$448.46		$479.4310	$479.43	$479.40	$479.50